CN111433000B - Polyamide film and method for producing same - Google Patents

Polyamide film and method for producing same Download PDF

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Publication number
CN111433000B
CN111433000B CN201880078001.4A CN201880078001A CN111433000B CN 111433000 B CN111433000 B CN 111433000B CN 201880078001 A CN201880078001 A CN 201880078001A CN 111433000 B CN111433000 B CN 111433000B
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film
polyamide
elastic modulus
stretching
thermoplastic elastomer
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CN111433000A (en
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大葛贵良
浜本彰子
赤松谦
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Unitika Ltd
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Unitika Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D7/00—Producing flat articles, e.g. films or sheets
    • B29D7/01—Films or sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/001—Combinations of extrusion moulding with other shaping operations
    • B29C48/0018—Combinations of extrusion moulding with other shaping operations combined with shaping by orienting, stretching or shrinking, e.g. film blowing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/07—Flat, e.g. panels
    • B29C48/08—Flat, e.g. panels flexible, e.g. films
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/10—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial
    • B29C55/12—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial
    • B29C55/16—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial simultaneously
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
    • B32B27/304—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising vinyl halide (co)polymers, e.g. PVC, PVDC, PVF, PVDF
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/34—Layered products comprising a layer of synthetic resin comprising polyamides
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/005—Shaping by stretching, e.g. drawing through a die; Apparatus therefor characterised by the choice of materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2067/00—Use of polyesters or derivatives thereof, as moulding material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2077/00—Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof, as moulding material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2007/00—Flat articles, e.g. films or sheets
    • B29L2007/008—Wide strips, e.g. films, webs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/30—Properties of the layers or laminate having particular thermal properties
    • B32B2307/306—Resistant to heat
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/40—Properties of the layers or laminate having particular optical properties
    • B32B2307/412—Transparent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
    • B32B2307/514—Oriented
    • B32B2307/518—Oriented bi-axially
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/724—Permeability to gases, adsorption
    • B32B2307/7242—Non-permeable
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2439/00—Containers; Receptacles
    • B32B2439/70—Food packaging
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2439/00—Containers; Receptacles
    • B32B2439/80—Medical packaging
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2327/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers
    • C08J2327/02—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment
    • C08J2327/04—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment containing chlorine atoms
    • C08J2327/08—Homopolymers or copolymers of vinylidene chloride
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2377/00—Characterised by the use of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Derivatives of such polymers
    • C08J2377/02—Polyamides derived from omega-amino carboxylic acids or from lactams thereof

Abstract

The invention provides a polyamide film, which is characterized in that the invention is a stretched film composed of a polyamide resin composition containing 1-10 mass% of polyester thermoplastic elastomer, and the stretched film satisfies all the following conditions (A) - (C). (A) The elastic modulus of the film in MD and TD is 1.0-2.3 GPa respectively. (B) The film has a ratio of the elastic modulus of MD to TD (MD/TD) of 0.9 to 1.5. (C) The haze of the film is 7% or less.

Description

Polyamide film and method for producing same
Technical Field
The present invention relates to a film made of a polyamide resin composition containing a polyester thermoplastic elastomer and a method for producing the same.
Background
Films made of polyamide resins such as nylon 6 and nylon 66 are excellent in mechanical properties such as tensile strength, puncture strength, pin hole strength, and impact strength, and are excellent in gas barrier properties and heat resistance. Therefore, laminated films obtained by laminating a sealant (sealant) made of a polyolefin film on a polyamide resin film as a base material by a method such as dry lamination or extrusion lamination are used in a wide range of fields including packaging materials for sterilization treatment such as boiling and retort (retorting).
In recent years, the performance of maintaining quality without deteriorating the packaged articles and contents has been increasingly required for packaging materials, and improvements thereof have been required. In particular, in the production, transportation, and consumption of contents such as pharmaceuticals and foods, a material distribution method (cold chain) for maintaining a low temperature environment is widely used to maintain quality, and improvement of pinhole resistance particularly in a low temperature environment is increasingly required for packaging materials.
The pinholes generated in the packaging material include puncture pinholes generated by puncturing the packaging material with respect to a target packaging material due to sharp corners of the packaging material, etc., bending pinholes generated by repeated bending of the packaging material due to vibration during transportation, etc., and friction pinholes generated by repeated contact with the corrugated cardboard box, etc. The polyamide resin film is considered to be a packaging material having high pinhole resistance, in which generation of pinholes due to such puncturing, bending, rubbing, and the like is small. However, since the polyamide resin film becomes hard when the ambient temperature is low, the number of pinholes generated by bending tends to increase significantly.
In order to improve the bending resistance in a low-temperature environment, a method of adding an olefin copolymer or a polyamide copolymer to a polyamide resin has been proposed.
For example, jp 2014-014976 a discloses a polyamide resin film having improved bending resistance in a low-temperature environment by adding a terpolymer of ethylene, n-butyl acrylate and maleic anhydride as an olefin copolymer. Further, jp 2003-012921 a discloses a polyamide resin in which a polyether ester amide elastomer as a polyamide thermoplastic elastomer is added as a polyamide copolymer to improve the bending resistance in a low-temperature environment.
However, none of the polyamide films has sufficiently improved bending resistance in a low-temperature environment and low transparency, and thus cannot be used for applications requiring transparency as a packaging material. As such, a packaging material excellent in bending resistance even under a low-temperature environment and excellent in transparency has not been provided yet.
Disclosure of Invention
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a polyamide film which has excellent bending resistance even in a low-temperature environment, is suitable for a medical container such as a food or an infusion bag to be refrigerated and circulated, and has excellent transparency, and a method for producing the same.
The present inventors have conducted studies to solve the above problems, and as a result, have found that a film obtained by forming and stretching a polyamide resin composition containing a specific amount of a polyester thermoplastic elastomer by a specific method has a specific elastic modulus and a specific elastic modulus ratio. Further, the present inventors have found that such a stretched film having a specific elastic modulus and an elastic modulus ratio is excellent in bending resistance in a low-temperature environment, can reduce the number of pinholes, and is also excellent in transparency, and have completed the present invention.
That is, the gist of the present invention is as follows.
(1) A polyamide film characterized by being a stretched film comprising a polyamide resin composition containing 1 to 10 mass% of a polyester thermoplastic elastomer, and satisfying all of the following conditions (A) to (C).
(A) The elastic modulus of the film in MD and TD is 1.0-2.3 GPa respectively.
(B) The film has a ratio of the elastic modulus of MD to TD (MD/TD) of 0.9 to 1.5.
(C) The haze of the film is 7% or less.
(2) The polyamide film according to (1), wherein the number of pinholes in 1000 repeated bending fatigue tests at 5 ℃ and 65% RH is 5/500 cm2The following.
(3) A polyamide-based laminated film characterized by having a polyvinylidene chloride-based resin layer on at least one surface of the polyamide-based film described in the above (1) or (2).
(4) A method for producing a polyamide film according to the above (1) or (2), characterized by sequentially carrying out the following steps (a) and (b).
(a) And a step of allowing an unstretched film made of a polyamide resin composition containing a polyester thermoplastic elastomer to absorb water so that the water content is 2 to 10%.
(b) And a step of biaxially stretching the unstretched film after water absorption so that the MD stretch ratio (X) and the TD stretch ratio (Y) are in the range of 2.2 to 3.8 times, respectively, and the ratio (X/Y) of the stretch ratios is 0.8 to 1.2.
(5) The method for producing a polyamide film according to item (4), wherein the unstretched film after water absorption is subjected to a preheating step at 180 to 250 ℃ and then biaxially stretched.
The polyamide film of the present invention contains a specific amount of a polyester thermoplastic elastomer and has a specific elastic modulus and a specific elastic modulus ratio, and therefore, has excellent bending resistance in a low-temperature environment, can reduce the number of pinholes, and has transparency.
Therefore, the polyamide film of the present invention can suppress the occurrence of pinholes in the filling step and the distribution step in a low-temperature environment, and can be used for polyamide resin packages and container bodies suitable for medical containers such as food and infusion bags that are distributed in a low-temperature environment.
The polyamide-based laminated film of the present invention has a polyvinylidene chloride-based resin layer on at least one surface of the polyamide-based film of the present invention, and has excellent gas barrier properties because the polyamide-based film of the present invention has high adhesion strength to the polyvinylidene chloride-based resin layer.
Detailed Description
The present invention will be described in detail below.
The polyamide film of the present invention is a stretched film composed of a polyamide resin composition containing a polyester thermoplastic elastomer. The polyamide resin layer of the polyamide film may have either a single-layer structure or a multilayer structure, and the single-layer structure is excellent in productivity.
Examples of the polyamide resin constituting the resin composition include nylon 6, nylon 66, nylon 46, nylon 69, nylon 610, nylon 612, nylon 1010, nylon 11, nylon 12, poly m-xylylene adipamide (nylon MXD6), nylon 6T, nylon 9T, nylon 10T, and mixtures and copolymers thereof.
Particularly, nylon 6 is preferable in terms of productivity and performance, and is excellent in cost performance. When nylon 6 is used as the film material, the other polyamide component in the polyamide resin may be contained by 30 mass% or less by a method such as copolymerization or mixing.
In order to suppress the formation of monomers during melting, the polyamide resin preferably contains an organic glycidyl ester, dicarboxylic anhydride, monocarboxylic acid such as benzoic acid, diamine, or the like as an end-capping agent.
The relative viscosity of the polyamide resin is not particularly limited, and is preferably 1.5 to 5.0, more preferably 2.5 to 4.5, and further preferably 3.0 to 4.0, as measured at a temperature of 25 ℃ and a concentration of 1g/dl using 96% sulfuric acid as a solvent. If the relative viscosity of the polyamide resin is less than 1.5, the mechanical properties of the resulting film tend to be significantly reduced. In addition, a polyamide resin having a relative viscosity of more than 5.0 is likely to hinder film formation.
The polyamide resin may contain, as necessary, 1 or 2 or more kinds of various additives such as a pigment, an antioxidant, an ultraviolet absorber, a preservative, an antistatic agent, an antiblocking agent, and inorganic fine particles within a range not adversely affecting the performance of the film.
The polyamide resin may contain 1 or 2 or more kinds of various inorganic lubricants and organic lubricants for the purpose of improving the sliding property of the film. Examples of the lubricant include clay, talc, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, calcium aluminate, magnesium aluminosilicate, glass spheres, carbon black, zinc oxide, antimony trioxide, zeolite, hydrotalcite, layered silicate, and ethylene bis stearamide.
The resin composition constituting the polyamide film of the present invention is required to contain 1 to 10% by mass of a polyester thermoplastic elastomer, preferably 1.5 to 8% by mass, and more preferably 2 to 6% by mass.
When the content of the polyester-based thermoplastic elastomer is less than 1% by mass, the elastic modulus of the obtained film is higher than the range specified in the present invention, and the bending resistance in a low-temperature environment is poor.
When the content of the polyester-based thermoplastic elastomer exceeds 10% by mass, the elastic modulus of the film obtained is lower than the range defined in the present invention, and the improvement of the bending resistance under a low-temperature environment corresponding to the content of the polyester-based thermoplastic elastomer is hardly observed, while the transparency is lowered. In addition, the puncture strength and abrasion resistance, which affect the pinhole resistance of the polyamide film, are also reduced.
The polyester-based thermoplastic elastomer of the present invention is preferably composed mainly of a crystalline polymer segment composed of a crystalline aromatic polyester unit and a polymer segment composed of an aliphatic polyether unit.
The crystalline polymer segment composed of a crystalline aromatic polyester unit is a unit composed of a crystalline aromatic polyester composed of an aromatic dicarboxylic acid or an ester-forming derivative thereof and an aliphatic diol, preferably a polybutylene terephthalate unit derived from terephthalic acid and/or dimethyl terephthalate and 1, 4-butanediol.
The polyester unit may be, in addition to the above, a polyester unit obtained from a dicarboxylic acid component such as terephthalic acid, isophthalic acid, phthalic acid, naphthalene-2, 6-dicarboxylic acid, naphthalene-2, 7-dicarboxylic acid, diphenyl-4, 4' -dicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sulfoisophthalic acid or an ester-forming derivative thereof, and a diol having a molecular weight of 300 or less, for example, an aliphatic diol such as 1, 4-butanediol, ethylene glycol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentyl glycol or decamethylene glycol, an alicyclic diol such as 1, 4-cyclohexanedimethanol or tricyclodecanehydroxymethyl, benzenedimethanol, bis (p-hydroxy) biphenyl, bis (p-hydroxyphenyl) propane, 2-bis [4- (2-hydroxyethoxy) phenyl ] propane, terephthalic acid, isophthalic acid, terephthalic acid, A polyester unit derived from an aromatic diol such as bis [4- (2-hydroxy) phenyl ] sulfone, 1-bis [4- (2-hydroxyethoxy) phenyl ] cyclohexane, 4 '-dihydroxy-p-terphenyl, 4' -dihydroxy-p-quaterphenyl, or a copolyester unit obtained by using 2 or more kinds of these dicarboxylic acid components and diol components in combination. Further, a polyfunctional carboxylic acid component having three or more functions, a polyfunctional oxoacid component, a polyfunctional hydroxyl component, and the like may be copolymerized in an amount of 5 mol% or less.
The polymer segment composed of aliphatic polyether units means units mainly composed of aliphatic polyethers. Specific examples of the aliphatic polyether include poly (ethylene ether) glycol, poly (propylene ether) glycol, poly (tetramethylene ether) glycol, poly (hexamethylene ether) glycol, a copolymer of ethylene oxide and propylene oxide, an ethylene oxide addition polymer of poly (propylene ether) glycol, a copolymer of ethylene oxide and tetrahydrofuran, and the like.
Among these aliphatic polyethers, poly (tetramethylene ether) glycol is preferable because the resulting polyester block copolymer has good elastic properties. The number average molecular weight of the polymer segment is preferably about 300 to 6000 in a copolymerized state.
The content of the polymer segment comprising an aliphatic polyether unit in the polyester-based thermoplastic elastomer is preferably 10 to 80% by mass, more preferably 15 to 75% by mass. When the content of the polymer segment is less than 10% by mass, the resulting resin composition tends to be hard, while when the content exceeds 80% by mass, the resin composition may be too soft to exhibit physical properties.
The polyester-based thermoplastic elastomer can be produced by a commonly used method. For example, a method in which a lower alcohol diester of a dicarboxylic acid, an excessive amount of a low molecular weight diol, and a component constituting a polymer segment are subjected to an ester exchange reaction in the presence of a catalyst to polycondense the obtained reaction product; a method in which a dicarboxylic acid, an excessive amount of a diol, and a component constituting a polymer segment are subjected to an esterification reaction in the presence of a catalyst to thereby obtain a reaction product, which is subjected to polycondensation; and a method of adding a polymer segment component to a crystalline segment prepared in advance and randomizing the resulting product by transesterification can be used.
Examples of commercially available products of the polyester-based thermoplastic elastomer include "PRIMALLOY AP" manufactured by mitsubishi chemical corporation, "perfrene" manufactured by tokyo spinnel corporation, and "HYTREL" manufactured by tokyo dupont corporation.
The elastic modulus of the polyamide film of the present invention in the MD (longitudinal direction) and TD (width direction) is required to be 1.0 to 2.3GPa, respectively, and the ratio of the elastic modulus of the MD to the elastic modulus of the TD (MD/TD) is required to be 0.9 to 1.5. The polyamide film of the present invention can improve the bending resistance in a low-temperature environment by satisfying the above-described ranges of the elastic modulus and the elastic modulus ratio of MD and TD, and can be a film excellent in transparency.
In general, in order to reduce the occurrence of pinholes in polyamide films, the characteristics of bending resistance, puncture strength and abrasion resistance are also important. The polyamide film of the present invention also has excellent puncture strength and abrasion resistance peculiar to polyamide films, and therefore exhibits excellent pinhole resistance even in a low-temperature environment.
The elastic modulus of the polyamide film of the present invention in both MD and TD is required to be 1.0 to 2.3GPa, preferably 1.2 to 2.1GPa, and more preferably 1.4 to 1.9GPa, as described above. When the elastic modulus of the polyamide film is lower than 1.0GPa, the bending resistance and transparency under a low-temperature environment are deteriorated, and the puncture strength and abrasion resistance are also deteriorated. On the other hand, if the elastic modulus of the polyamide film is higher than 2.3GPa, even if the polyester elastomer is contained in the range specified in the present invention, the bending resistance under low temperature environment is poor, or the transparency is poor.
The polyamide film of the present invention has a ratio of the elastic modulus of MD to TD (MD/TD) of 0.9 to 1.5, preferably 1.0 to 1.4, and more preferably 1.1 to 1.35 as described above. If the elastic modulus ratio deviates from the range specified in the present invention, the bending resistance and transparency under low temperature environment are poor, and the puncture strength and abrasion resistance are also reduced.
The production of the polyamide film having the elastic modulus and the elastic modulus ratio defined in the present invention can be carried out by the method for producing a film of the present invention described later.
The haze, which is a characteristic value indicating the transparency of the polyamide film of the present invention, needs to be 7% or less, preferably 5% or less, and more preferably 3.3% or less. Polyamide films having a haze of more than 7% are difficult to use in applications requiring transparency. In addition, a polyamide film having a haze of more than 7% may have an insufficient dispersed state of the polyester thermoplastic elastomer or insufficient preheating before the stretching step in the film production. That is, the elastic modulus may exceed the range specified in the present invention, or the bending resistance in a low-temperature environment may be lowered.
The bending resistance of the polyamide-based film of the present invention in a low temperature environment was evaluated by the number of pinholes in 1000 repeated bending fatigue tests using a gelbo flex tester under an atmosphere of 5 ℃ and 65% RH. The number of the polyamide-based film of the present invention is preferably 5/500 cm2Among them, 3.5 pieces/500 cm are more preferable2The following. The number of pinholes exceeds 5/500 cm2The polyamide film of (2) has a problem that the strength is insufficient when forming a package, and particularly, pinholes occur as a result of bending fatigue in a low-temperature environment, and leakage occurs when the content is a liquid.
As described above, the polyamide film of the present invention is excellent in both puncture strength and abrasion resistance, which are characteristics that affect pinhole resistance in a low-temperature environment.
First, the puncture strength of the polyamide film of the present invention in a low temperature environment was evaluated by the puncture strength in an atmosphere of 5 ℃ and 65% RH. The strength of the polyamide-based film of the present invention is preferably 0.60N/μm or more, more preferably 0.65N/μm or more, per 1 μm. Polyamide films having a puncture strength of less than 0.60N/. mu.m are sometimes difficult to use in applications requiring pinhole resistance.
The abrasion resistance of the polyamide film of the present invention in a low temperature environment was evaluated by the number of times of sliding until pinholes were generated by repeated contact in an atmosphere of 5 ℃ and 65% RH using a chemical vibration type friction tester. The number of times of the polyamide-based film of the present invention is preferably 200 or more, more preferably 250 or more. If the number of sliding until pinhole occurrence is less than 200, it may be difficult to use the film for applications requiring pinhole resistance.
The thickness of the polyamide film of the present invention is preferably 10 to 50 μm when used for packaging.
Next, a method for producing the polyamide film of the present invention will be described.
The polyamide film of the present invention can be produced by a sheet molding step of molding a melt-kneaded product containing a polyamide resin and a polyester thermoplastic elastomer into a sheet to obtain an unstretched film, a step of allowing the unstretched film to absorb water at a specific water content, and a stretching step of stretching the unstretched film after water absorption at a specific ratio of magnification to magnification in MD and TD.
First, a polyamide resin and a polyester thermoplastic elastomer are melt-kneaded to produce a polyamide resin composition.
The extruder used for melt kneading may be a single-screw extruder having 1 screw in the barrel or a multi-screw extruder having a plurality of screws. In addition, when the polyester-based thermoplastic elastomer and the polyamide resin are charged into the cylinder, they are preferably simultaneously charged from the vicinity of the inlet of the cylinder, but the polyester-based thermoplastic elastomer may be charged from the vicinity of the inlet of the cylinder and then the polyamide resin may be charged from the middle of the cylinder.
In either case, it is preferable to melt-knead the composition immediately after the two resins are put into the mixer by setting the cylinder temperature at the start of kneading to 180 to 200 ℃ and setting the cylinder temperature in the vicinity of the outlet of the composition in which the two resins are kneaded to (melting point of polyamide resin +10 ℃) to (melting point of polyamide resin +30 ℃).
By melt-kneading at such a temperature setting, the dispersibility of the polyester-based thermoplastic elastomer added to the polyamide resin is improved.
When the cylinder temperature at the start of kneading is less than 180 ℃, the melt of the polyamide resin is transferred to the rear half of the cylinder, and kneading with the polyester-based thermoplastic elastomer becomes insufficient, and the dispersed particle size of the polyester-based thermoplastic elastomer becomes large, and thus the film obtained may have insufficient bending resistance or increased haze. On the other hand, when the cylinder temperature at the start of kneading exceeds 200 ℃, the polyester thermoplastic elastomer is melted and wound around the cylinder immediately after charging, and the extrusion of the polyamide resin may become unstable, and it may be difficult to form an unstretched film having a uniform film thickness.
Further, when the cylinder temperature near the outlet of the composition in which the two resins are mixed is lower than (melting point of polyamide resin +10 ℃), there is a possibility that the polyamide resin is not melted, and it may be difficult to form a continuous unstretched film. On the other hand, when the cylinder temperature in the vicinity of the outlet exceeds (melting point of polyamide resin +30 ℃), the polyamide resin or polyester thermoplastic elastomer may be thermally decomposed, and it may be difficult to form a continuous unstretched film.
Next, the resin composition containing the two resins is heated and melted by an extruder, extruded from a T-die into a film, and cooled and solidified on a rotating cooling drum by a known casting method such as an air knife casting method or an electrostatic application casting method to form an unstretched film.
The average thickness of the unstretched film is not particularly limited, but is generally about 15 to 500 μm, preferably 50 to 300 μm. By setting the amount within such a range, the stretching step can be more effectively performed.
In the production method of the present invention, the step (a) of absorbing water in the obtained unstretched film so that the water content is 2 to 10 mass% is required.
The water content of the unstretched film before water absorption was usually 0.1 mass%, and conventionally, the unstretched film having such a water content was stretched. In contrast, the present invention is characterized in that the water content is adjusted to the above range by adding water to the unstretched film.
That is, in the present invention, the water content of the unstretched film is required to be 2 to 10 mass%, and preferably 3.5 to 8.5 mass%, as described above. If the water content of the unstretched film is less than 2 mass%, the water content of the plasticizer is small, and therefore the stress during stretching becomes high. Therefore, large voids or a plurality of voids are generated between the polyamide resin and the dispersed polyester thermoplastic elastomer particles in the film, the haze of the film increases, or the film is often broken. On the other hand, if the water content exceeds 10 mass%, the non-stretched film will have large thickness unevenness, and the stretched film obtained through the stretching step will also have large thickness unevenness, resulting in poor bending resistance.
The method for adjusting the moisture content is not particularly limited as long as the moisture content of the unstretched film can be increased. For example, any of a method of spraying water or steam to the unstretched film, a method of applying water to the unstretched film with a roll, a method of immersing the unstretched film in water, and the like may be used. For example, a method of immersing an unstretched film in a water tank for a certain period of time may be suitably employed.
The water used for adjusting the water content may be any of pure water, tap water, and the like, and is not particularly limited. In addition, other components may be dispersed or dissolved in water as long as the effects of the present invention are not hindered. The pH of water used for adjusting the water content is preferably 6.5 to 9.0.
The temperature of the water is preferably 20-70 ℃, more preferably 30-65 ℃, and further preferably 40-55 ℃. When the temperature of water is less than 20 ℃, it may be difficult to adjust the water content in a short time. If the temperature of water exceeds 70 ℃, the unstretched film tends to wrinkle, resulting in uneven stretching, resulting in a decrease in the quality of the stretched film, and problems such as film breakage during stretching, and displacement of the film ends between the clips tend to occur, resulting in a decrease in the workability.
The time for immersing the unstretched film in the water bath is preferably 0.5 to 10 minutes.
The unstretched film that absorbs water so that the moisture percentage is 2 to 10 mass% is preferably subjected to a step of preheating before the stretching step. The preheating temperature is preferably 180-250 ℃, more preferably 190-240 ℃, and further preferably 200-230 ℃.
When the preheating temperature is less than 180 ℃, the unstretched film is difficult to obtain a film temperature necessary for stretching, and therefore, the stretching stress is high, and the polyamide resin closely adhered to the polyester-based thermoplastic elastomer is rapidly peeled off by the stretching stress, and a large void or a plurality of voids are generated in the film, and therefore, the void ratio is high, and the haze is increased in some cases. In addition, neck stretching occurs, or bowing phenomenon becomes remarkable, or breakage often occurs.
On the other hand, when the preheating temperature exceeds 250 ℃, the evaporation rate of the water absorbed in the unstretched film becomes high, and therefore, the film temperature becomes too high, elongation (draw) stretching occurs, and molecular orientation becomes difficult, and therefore, the obtained stretched film tends to have uneven thickness and poor bending resistance.
The method of preheating the unstretched film is not limited. For example, it is preferable to set the temperature of hot air blown to the film traveling in the preheating zone of the stretching machine to the above temperature range. The time for the unstretched film to travel in the preheating region (preheating time) is preferably 0.5 to 5 seconds.
Next, the unstretched film absorbing water in the above-described manner is stretched in a stretching step.
The stretching method is not particularly limited, and for example, a tubular method, a tenter simultaneous biaxial stretching method, a tenter sequential biaxial stretching method, and the like can be cited. The tubular method is advantageous in that it is cheaper than other methods in terms of equipment cost, but it is difficult to improve the thickness accuracy of the film, and the tenter-type biaxial stretching method is excellent in terms of quality stability, dimensional stability, and productivity. Therefore, the tenter biaxial stretching method is preferable as the method for producing the polyamide film of the present invention, and particularly, the tenter simultaneous biaxial stretching method tends to reduce variations in physical property values and strains between the center portion and the end portions of the film, and is therefore preferable as the method for producing a film having the elastic modulus and the elastic modulus ratio defined in the present invention.
As described above, by performing the stretching and heat-setting treatment after the unstretched film is set to a specific moisture content, the tensile stress during stretching can be suppressed, the polyamide resin in close contact with the polyester-based thermoplastic elastomer can be stretched without peeling due to the tensile stress, and the occurrence of large voids or the occurrence of a plurality of voids in the film can be effectively suppressed or prevented.
In the production method of the present invention, it is necessary to perform the step (b) of subjecting the unstretched film, which has absorbed water by passing through the step (a), to biaxial stretching so that the stretching magnification (MD stretching magnification, X) in the longitudinal direction and the stretching magnification (TD stretching magnification, Y) in the width direction are in the range of 2.2 to 3.8 times, respectively, and the ratio (X/Y) of the stretching magnifications is 0.8 to 1.2. Wherein X and Y are respectively preferably 2.3-3.7 times, and X/Y is preferably 0.9-1.1.
If either of X and Y is less than 2.2 times, the unstretched film is not sufficiently stretched, and the stretched film thus obtained does not sufficiently undergo oriented crystallization of the film, with the result that the elastic modulus becomes low and the thickness unevenness becomes large. As a result, the bending resistance is poor, and the impact strength, tensile elongation, and the like are also poor in some cases. On the other hand, if either X or Y exceeds 3.8 times, oriented crystallization of the film excessively proceeds, and as a result, the elastic modulus of the obtained stretched film tends to be high, and the film tends to break in the stretching step.
If the ratio of the stretching magnification (X/Y) deviates from the above range, the anisotropy of the elastic modulus of the obtained stretched film tends to increase, and the bending resistance and the abrasion resistance tend to decrease.
The product of the draw ratios (X Y) is preferably 8.5 to 11.0, more preferably 9.0 to 10.0. If the product of the stretch ratios (X Y) is less than 8.5, the elastic modulus of the resulting stretched film may be low, and the abrasion resistance may be low. On the other hand, if the product of the stretch ratios (X × Y) exceeds 11.0, the elastic modulus of the resulting stretched film may be high, and the bending resistance may be low.
The preferable stretching temperature is 170-230 ℃, and the more preferable stretching temperature is 180-220 ℃. When the stretching temperature is less than 170 ℃, the film temperature required for stretching is not easily obtained, so that the tensile stress becomes high, physical properties such as bending resistance and impact strength of the stretched film are lowered, and breakage often occurs. On the other hand, when the stretching temperature exceeds 230 ℃, the film temperature becomes too high, and elongation stretching is performed, and molecular orientation is not easily performed, and therefore, physical properties such as impact strength of the obtained stretched film are degraded.
The biaxially stretched film is heat-set at a temperature of 150 to 220 ℃ in a tenter subjected to stretching treatment, and preferably subjected to MD and/or TD relaxation treatment in a range of 0 to 10%, preferably 2 to 6%, as required.
The polyamide film of the present invention may have a functional layer such as a gas barrier coating layer or a sealant layer laminated on at least one surface thereof. The resin constituting the gas barrier coating layer is not particularly limited, and is preferably a polyvinylidene chloride-based resin (PVDC).
The polyamide-based laminated film of the present invention has a PVDC layer on at least one surface of the polyamide-based film of the present invention. The PVDC is obtained as a latex dispersed in a medium by polymerizing 50 to 99 mass% of vinylidene chloride as a raw material and 1 to 50 mass% of 1 or more other monomers copolymerizable with vinylidene chloride by a known emulsion polymerization method. The average particle diameter of PVDC in the latex is preferably 0.05-0.5 μm, and particularly preferably 0.07-0.3 μm. The PVDC may be used in combination with various additives such as an antiblocking agent, an antistatic agent and the like within a range not to impair the effects of the present invention.
The thickness of the PVDC layer is preferably 0.5 to 3.5 μm, more preferably 0.7 to 3.0 μm, and still more preferably 1.0 to 2.5 μm. If the thickness of the PVDC layer is less than 0.5 μm, the gas barrier property cannot be sufficiently obtained, and if it exceeds 3.5 μm, the film forming property is lowered and the appearance of the film is easily impaired. Further, if the PVDC layer becomes thick, the laminated film tends to be hard, and therefore pinholes tend to be generated by bending in a low-temperature environment.
The adhesion strength of the polyamide-based laminated film to the PVDC layer is preferably 0.8N/cm or more, more preferably 1.0N/cm or more, and still more preferably 2.0N/cm or more. If the adhesion strength is less than 0.8N/cm, the polyamide-based laminated film may be peeled off from the PVDC layer during boiling treatment or retort treatment, or sufficient sealing strength may not be obtained.
If the amount of the monomer or the content of the polyester thermoplastic elastomer in the polyamide film is large, the adhesion strength between the polyamide film and the PVDC layer may be reduced.
The PVDC layer is preferably formed on the polyamide film in a stage where the amount of monomer is small after the moisture content adjustment step and before stretching, thereby improving the adhesion strength to the polyamide film.
The method for coating the PVDC latex to laminate the PVDC layer on the polyamide film is not particularly limited, and a general method such as gravure roll coating, reverse roll coating, wire bar coating, air knife coating, die coating, curtain die coating, or the like can be used.
The polyamide film may be subjected to corona discharge treatment or the like immediately before the coating.
The thickness of the polyamide-based laminated film is preferably in the range of 10 to 30 μm when used for packaging.
The polyamide-based laminated film of the present invention in which a PVDC layer is laminated on a polyamide-based film has excellent pinhole resistance in a low-temperature environment, has excellent gas barrier properties, and has excellent adhesion between the polyamide-based film and the PVDC layer, and therefore can be suitably used as a packaging material.
Examples
The present invention will be specifically described below with reference to examples. The following examples and comparative examples were evaluated for various physical properties in the following manner.
Relative viscosity
Pellets of the polyamide resin were dissolved in 96% sulfuric acid to a concentration of 1g/dl, and measured at a temperature of 25 ℃.
< Water Rate >
An unstretched film before stretching was collected, placed in a weighing bottle, dried at 150 ℃ for 20 hours, and calculated from the change in mass before and after drying.
< operability >
The state of the unstretched film passing through the water tank was visually observed to determine the occurrence of wrinkles, snaking, and the like. Evaluation was performed in three stages of "o", "Δ", and "x" described below, and "o" and "Δ" were defined as "acceptable".
Good: the running unstretched film is free from wrinkles, snaking, etc
And (delta): although the film can be stretched, wrinkles, meandering, and the like occur in the running unstretched film
X: wrinkles, meandering, and the like frequently occur in the running unstretched film, and breakage of the stretched film frequently occurs
< elastic modulus, elastic modulus ratio >
The obtained polyamide film and polyamide laminated film were allowed to stand in an environmental test chamber adjusted to 23 ℃ and 50% RH for 2 hours, and then cut into a long strip shape having a measuring direction of MD and TD of 300mm (a distance between the reticle lines of 250mm) and a direction perpendicular to the measuring direction of 15mm, to obtain a sample. A tensile test was carried out at a test speed of 500mm/min using a tensile tester (AG-IS, manufactured by Shimadzu corporation) equipped with a load cell for measuring 1kN and a sample chuck. The elastic modulus was calculated from the slope of the load-elongation curve, and the elastic modulus ratio (MD/TD) was calculated. The number of samples was measured by 5, and the average value was calculated.
< haze >
The total haze was measured in accordance with ASTM D1003-61 using a haze meter manufactured by Tokyo electrochromatics. The number of samples was measured in 3, and the average value was calculated.
< flexural resistance (pinhole resistance 1) (flexural fatigue test) >)
The obtained polyamide film or polyamide laminated film was left in an environmental test room adjusted to 5 ℃ and 65% RH for 2 hours, and then subjected to 1000 bending fatigue tests (torsion angle 440 °) using a gelbo flex TESTER (manufactured by ster industries, BE-1005). For the film sample (distance between chucks 178mm, diameter 89mm), by passing throughThe number of pinholes was determined by measuring the number of ink-transmitting sites on the filter paper. The number of samples was measured by 3 and the calculation was made for each 500cm2Average value of the number of pinholes in (1).
< puncture Strength (pinhole resistance 2) >)
The obtained polyamide film or polyamide laminated film was left in an environmental test chamber adjusted to 5 ℃ and 65% RH for 2 hours, and then the film was fixed to a circular mold frame having an inner diameter of 100mm by pulling the film, and a needle having a radius of curvature of 0.5mm at the tip was inserted into the center of the sample perpendicularly to the surface of the sample at a rate of 50 mm/min to measure the strength at the time of film breakage. The number of samples was measured by 5, and the average value of the intensity value per 1 μm thickness of the film was calculated.
< abrasion resistance (pinhole resistance 3) >)
The obtained polyamide film or polyamide laminated film was left in an environmental test chamber adjusted to 5 ℃ and 65% RH for 2 hours, then folded into four folds, and the apex and the basis weight of the folded film were adjusted to 400g/m in a chemical vibration type friction tester2After the cardboard sheet was hung down, a load of 50g was applied to the film and fixed to a jig. The cardboard was slid at 120mm and 30 times/min in the longitudinal direction of the folded film, and the number of slides until pinholes were formed was measured. The test was performed with 3 samples, and the generation of pinholes was confirmed every 20 slides. The abrasion resistance was evaluated by the number of sliding times at the time when pinholes occurred in all samples. For example, when pinholes were generated in all of 3 samples when the number of sliding was 400, and in 2 of 3 samples when the number of sliding was 380, the abrasion resistance was evaluated as 400.
The presence or absence of the generation of pinholes was judged by dropping ethyl acetate at the apex of the folded film in contact with the cardboard and by the presence or absence of ethyl acetate penetration on the white paper.
< uneven thickness >
The thickness was measured every 10cm along the width direction of the polyamide film and over the entire width using a β -ray transmission type thickness meter, the thickness unevenness was calculated from the following formula, and the evaluation was performed in the following 3 stages, and "∘" and "Δ" were defined as being acceptable.
Thickness unevenness (maximum thickness in width direction-minimum thickness in width direction) ÷ average thickness × 100
Good: less than 10%
And (delta): more than 10% and 15% or less
X: more than 15 percent
< oxygen permeability >
The gas barrier property was evaluated by measuring the oxygen permeability of the polyamide-based laminated film in an atmosphere at a temperature of 20 ℃ and 85% RH using an oxygen barrier measuring instrument (OX-TRAN 2/20) manufactured by MOCON corporation. The number of samples was measured by 2 and the average value was calculated. If the oxygen permeability is less than 110 ml/(m)2d.MPa), the product is qualified.
< sealing Strength >
The dry coating weight of the PVDC layer of the polyamide laminated film was 3.0g/m2A urethane adhesive (Dicdry LX-401A/SP-60, product of DIC) was applied, followed by heat treatment at 80 ℃. Then, an unstretched polyethylene film (T.U.X FCS, 50 μm, manufactured by Mitsui Chemicals Tohcello Co., Ltd.) was dry-laminated on the heat-treated adhesive surface with a nip pressure of 490kPa on a metal roll heated to 80 ℃. Further, the adhesive is cured as recommended to obtain a laminated film.
A test piece having a width of 15mm was taken from the obtained laminated film, and the interface between the polyethylene film and the PVDC layer was peeled off from the end of the test piece in an atmosphere of 65% RH at 20 ℃. Then, the laminate strength was measured by using a tensile tester (AGS-100G manufactured by Shimadzu corporation) at a tensile rate of 300mm/min so that the polyethylene film and the polyamide-based laminated film were formed into a T-shape.
In this lamination strength measurement, peeling occurred at the interface between the PVDC layer and the polyamide film, or at the interface between the polyethylene film and the PVDC layer. In the samples after the strength measurement, when the interlayer between the polyamide film and the PVDC layer is not peeled off, the peel strength between the polyamide film and the PVDC layer is considered to have at least a value equal to or higher than the measured value. The adhesion strength was 0.8N/cm or more and was regarded as acceptable.
The raw materials used in the examples and comparative examples are as follows.
[ Polyamide resin ]
100 parts by mass of epsilon-caprolactam, 0.12 parts by mass of benzoic acid (10 mmol/kg per epsilon-caprolactam) and 3 parts by mass of water were charged into a closed reaction vessel equipped with a stirrer, the temperature was raised, a polycondensation reaction was carried out at a pressing force of 0.5MPa and a temperature of 260 ℃, the reaction vessel was discharged, the reaction vessel was cut into chips (chips), and the chips were refined and dried to obtain a polyamide resin. The relative viscosity of the chips of the polyamide resin was 3.03.
[ Master chip ]
100 parts by mass of a polyamide resin and 6 parts by mass of fine silica particles (Syloid SY-150, product of Shuizui chemical Co., Ltd.) were melt-mixed to prepare master batch chips.
[ polyester-based thermoplastic elastomer ]
PRIMALLOY: PRIMALLOY AP GQ131 manufactured by Mitsubishi chemical corporation
HYTREL: HYTREL 5577, manufactured by Toronto corporation
[ Polyamide-based thermoplastic elastomer ]
PEBAX: PEBAX 3533 manufactured by Arkema corporation
[ olefin copolymer ]
REXPEARL: REXPEARL ET230X manufactured by Japan polyethylene Co
Example 1
The polyamide resin, the PRIMALLOY of the polyester thermoplastic elastomer and the master batch chips were blended so that the PRIMALLOY content became 5.0 mass% and the inorganic fine particles content became 0.05 mass%, and the mixture was fed into an extruder, melted in a cylinder heated to a temperature of 190 ℃ at the start of kneading and a temperature of 230 ℃ at the outlet of the cylinder, extruded from a T-die orifice into a sheet, and cooled to 10 ℃ and cooled rapidly to obtain an unstretched film having a thickness of 250 μm.
Next, as a moisture content adjusting step, the unstretched film was introduced into a water tank set to ph7.9 and a temperature of 53 ℃, and immersed in water for 1 minute, thereby absorbing water so that the moisture content of the film became 6.3 mass%.
Subsequently, the unstretched film after water absorption was introduced into a simultaneous biaxial stretcher, subjected to a preheating treatment at 210 ℃ for 2 seconds as a preheating step, and then subjected to simultaneous biaxial stretching at 195 ℃ for 2 seconds at a MD stretching ratio (X) of 3.0 and a TD stretching ratio (Y) of 3.3. Subsequently, the sheet was subjected to a heat-setting treatment at 220 ℃ for 5 seconds and then to a relaxation treatment of 5% in the transverse direction, thereby obtaining a polyamide film having a thickness of 25 μm.
Examples 2 to 15 and comparative examples 1, 3 to 14
A polyamide film having a thickness of 25 μm was obtained in the same manner as in example 1, except that the type and content of the elastomer and the film production conditions were changed as shown in table 1.
In example 11, the conditions of the moisture content adjusting step were changed, and the moisture content of the unstretched film after water absorption was adjusted to 2.8% by mass by drying the unstretched film at 80 ℃ for 30 seconds by an infrared irradiation machine. In examples 12 and 13 and comparative example 14, the thickness of the unstretched film was changed by changing the stretching ratio of the unstretched film, and a polyamide film having a thickness of 25 μm was obtained. In example 14, the unstretched film was 150 μm thick to obtain a polyamide film 15 μm thick. In comparative example 8, a polyamide film was obtained without performing the moisture content adjusting step. In comparative example 9, the unstretched film after water absorption was dried at 110 ℃ for 30 seconds by an infrared irradiation machine to adjust the moisture content of the unstretched film to 1.2 mass%.
Example 16
An unstretched film having a thickness of 250 μm was obtained in the same manner as in example 1.
Next, as a water content adjustment, the unstretched film was introduced into a water tank set to ph7.9 and a temperature of 53 ℃, immersed in water for 1 minute, and then dried for 30 seconds by an infrared irradiation machine at a temperature of 80 ℃, to prepare an unstretched film having a film water content of 2.8 mass%.
Subsequently, the unstretched film after water absorption was longitudinally stretched at 55 ℃ and an MD stretching ratio (X) of 2.8 times by an MD stretcher comprising a heating roller group having different peripheral speeds.
Subsequently, the longitudinally stretched film was subjected to a preheating treatment at 180 ℃ for 1 second, and then subjected to a transverse stretching treatment at 180 ℃ at a TD stretching ratio (Y) of 3.5 times, thereby successively performing stretching treatments.
Then, the temperature was gradually raised in a tenter and heat treatment was performed at a maximum reaching temperature of 210 ℃, and further relaxation was performed at 210 ℃ in TD by 2%. Then, the film was cooled at 100 ℃ to obtain a polyamide film having a thickness of 25 μm.
Comparative example 2
A polyamide film having a thickness of 25 μm was obtained in the same manner as in example 16, except that no PRIMALLOY was added.
Comparative example 15
A polyamide film having a thickness of 25 μm was obtained in the same manner as in example 16, except that the MD stretching ratio (X) was changed to 3.0 times and the TD stretching ratio (Y) was changed to 4.0 times.
The compositions, production conditions, and evaluation results of the polyamide films obtained in examples 1 to 16 and comparative examples 1 to 15 are shown in table 1.
[ Table 1]
Figure BDA0002520067460000171
As is clear from table 1, the polyamide films of examples 1 to 16 have excellent bending resistance in a low temperature environment, excellent puncture strength and abrasion resistance, and excellent pinhole resistance because the content of the polyester thermoplastic elastomer and the production conditions are appropriate. And has a small haze value and excellent transparency.
On the other hand, the films of comparative examples 1 and 2 do not contain the polyester thermoplastic elastomer, and the content of the polyester thermoplastic elastomer in the film of comparative example 3 is less than the range defined in the present invention, so that both the elastic modulus and the elastic modulus ratio have values higher than the range defined in the present invention. Therefore, the bending resistance in a low-temperature environment is poor.
In the film of comparative example 4, the content of the polyester-based thermoplastic elastomer was more than the range defined in the present invention, and therefore, the elastic modulus of the film was a value lower than the range defined in the present invention. Therefore, the haze value is high, the transparency is deteriorated, and the abrasion resistance is also lowered. Further, in the moisture content adjusting step, wrinkles are generated in the running unstretched film, and the running of the film becomes unstable, thereby deteriorating the workability.
The film of comparative example 5 contains an amide-based thermoplastic elastomer instead of a polyester-based thermoplastic elastomer, and therefore, although the transparency is good, the bending resistance in a low-temperature environment is poor. The film of comparative example 6 had a high haze value and poor transparency, although the bending resistance in a low-temperature environment was good because the content of the amide-based thermoplastic elastomer was 8.0 mass%. In addition, the abrasion resistance of the film is also reduced. From the results of comparative examples 5 and 6, it is clear that even when the polyamide film contains the amide thermoplastic elastomer, both the bending resistance and the transparency in the low-temperature environment cannot be achieved.
Since the film of comparative example 7 contains an ethylene copolymer instead of a polyester thermoplastic elastomer, wrinkles were generated in the running unstretched film in the moisture content adjustment step, and stretching was not uniform, so that breakage was frequently generated, and a film could not be obtained.
The film of comparative example 8 did not pass through the water fraction adjustment step, and therefore the elastic modulus of the film had a value higher than the range specified in the present invention. Therefore, the bending resistance in a low-temperature environment is poor, the haze is increased, and the transparency is lowered.
The film of comparative example 9 was produced by stretching an unstretched film having a moisture content lower than the range defined in the present invention, and therefore the elastic modulus of the film was higher than the range defined in the present invention. Therefore, the bending resistance in a low-temperature environment is poor, the haze is increased, and the transparency is lowered.
The film of comparative example 10 was produced by stretching an unstretched film having a moisture content higher than the range defined in the present invention, which was obtained in the same manner as in example 1 except that the treatment time was changed to 11 minutes in the moisture content adjustment step, and therefore, the elastic modulus had a value lower than the range defined in the present invention, and the thickness unevenness was large. Therefore, the bending resistance in a low-temperature environment is poor, and the abrasion resistance is also reduced.
Since the film of comparative example 11 was produced under the condition of low preheating temperature, the haze was increased and the transparency was lowered.
The film of comparative example 12 was produced under the condition of high preheating temperature, and the ratio (X/Y) of the stretch ratio of the film of comparative example 13 was larger than the range specified in the present invention, so that the elastic modulus of the film was lower than the range specified in the present invention, and the thickness unevenness was also large. Therefore, the bending resistance in a low-temperature environment is poor, and the abrasion resistance is also reduced.
The TD stretching ratio (Y) of the film of comparative example 14 is smaller than the range defined in the present invention, and therefore the elastic modulus of the film is lower than the range defined in the present invention, and the thickness unevenness is also large. Therefore, the bending resistance in a low-temperature environment is poor, and the abrasion resistance is also reduced.
The TD stretching ratio (Y) of the film of comparative example 15 is larger than the range defined in the present invention, and the ratio (X/Y) of the stretching ratios is smaller than the range defined in the present invention, so that the elastic modulus and the elastic modulus ratio are values exceeding the range defined in the present invention. Therefore, the bending resistance in a low-temperature environment is poor, the haze is high, and the transparency is lowered.
Example 17
An unstretched film having a thickness of 250 μm was obtained in the same manner as in example 1.
Next, as a water content adjusting step, the unstretched film was introduced into a water tank set to ph7.9 and a temperature of 53 ℃, and immersed in water for 1 minute.
Subsequently, one side of the water-absorbed unstretched film was coated with PVDC Latex (Saran Latex L536B (solid content concentration 49 mass%) by an air knife coating method, and dried by an infrared irradiation machine at 110 ℃ for 30 seconds to evaporate water in the Latex.
This latex was applied, and an unstretched film having moisture in the latex dried (moisture content 5.8 mass%) was introduced into a simultaneous biaxial stretching machine, and simultaneous biaxial stretching was performed at a MD stretching ratio (X) of 3.0 times and a TD stretching ratio (Y) of 3.3 times. Subsequently, heat treatment was performed at 210 ℃ to perform 5% relaxation treatment in the transverse direction, thereby obtaining a polyamide laminated film having a thickness of 25 μm of the stretched polyamide film and a thickness of 1.5 μm of the PVDC layer.
Examples 18 to 27 and comparative examples 16 to 21
A polyamide-based laminated film was obtained in the same manner as in example 17, except that the thickness of the PVDC layer, the content of the polyester-based thermoplastic elastomer, the kind of the PVDC latex, and the production conditions were changed to the values shown in tables 2 and 3.
The structures, production conditions, and evaluation results of the polyamide-based laminated films obtained in examples 17 to 27 and comparative examples 16 to 21 are shown in tables 2 and 3.
[ Table 2]
Figure BDA0002520067460000201
[ Table 3]
Figure BDA0002520067460000211
As is clear from tables 2 and 3, the polyamide films of examples 17 to 27 have excellent bending resistance in a low temperature environment, excellent puncture strength and abrasion resistance, and excellent pinhole resistance, because the content of the polyester-based thermoplastic elastomer and the production conditions are appropriate. And has a small haze value and excellent transparency. In addition, the polyamide film has excellent adhesion strength to the PVDC layer and also has excellent gas barrier properties.
The laminate film of comparative example 16 has a higher elastic modulus than the range defined in the present invention because the polyamide film does not contain a polyester thermoplastic elastomer. Therefore, the bending resistance in a low-temperature environment is poor.
In the laminate film of comparative example 17, the content of the polyester thermoplastic elastomer in the polyamide film is larger than the range defined in the present invention, and therefore the elastic modulus of the film is a value lower than the range defined in the present invention. Therefore, the film had high haze and poor transparency. Further, the abrasion resistance is also lowered, and the adhesion strength between the PVDC layer and the polyamide film is also lowered.
The laminated film of comparative example 18 was produced under the condition of low preheating temperature, and thus had high haze and poor transparency.
Since the laminated film of comparative example 19 was produced under the condition of high preheating temperature, the elastic modulus of the film was lower than the range specified in the present invention, and the thickness unevenness was also large. Therefore, the bending resistance in a low-temperature environment is poor, and the abrasion resistance is also reduced.
In the laminate film of comparative example 20, both the MD stretching ratio (X) and the ratio of the stretching ratio (X/Y) are larger than the ranges defined in the present invention, and therefore the elastic modulus exceeds the range defined in the present invention, and the bending resistance in a low-temperature environment is poor.
The laminate film of comparative example 21 has a lower ratio of the elastic modulus to the elastic modulus than the range defined in the present invention because the ratio of the stretch ratio (X/Y) is smaller than the range defined in the present invention. Therefore, the bending resistance in a low-temperature environment is poor, and the abrasion resistance is also poor.

Claims (5)

1. A polyamide film characterized by being a stretched film comprising a polyamide resin composition containing 1 to 10 mass% of a polyester thermoplastic elastomer, and satisfying all of the following conditions (A) to (C),
(A) the elastic modulus of the film in MD and TD is 1.0-2.3 GPa respectively,
(B) the ratio of the elastic modulus of the film between MD and TD, that is, MD/TD, is 0.9 to 1.5,
(C) the haze of the film is 7% or less.
2. The polyamide-based film according to claim 1, wherein the number of pinholes in 1000 repeated bending fatigue tests at 5 ℃ and 65% RH is 5/500 cm2The following.
3. A polyamide-based laminate film characterized by comprising a polyvinylidene chloride-based resin layer on at least one surface of the polyamide-based film according to claim 1 or 2.
4. A method for producing a polyamide film according to claim 1 or 2, comprising the steps of (a) and (b) in this order,
(a) a step of allowing an unstretched film made of a polyamide resin composition containing a polyester thermoplastic elastomer to absorb water so that the water content is 2 to 10%,
(b) and a step of biaxially stretching the unstretched film after water absorption so that X, which is an MD stretch ratio, and Y, which is a TD stretch ratio, are in the range of 2.2 to 3.8 times, respectively, and X/Y, which is a ratio of the stretch ratios, is 0.8 to 1.2.
5. The method for producing a polyamide film according to claim 4, wherein the unstretched film after water absorption is subjected to a preheating step at 180 to 250 ℃ and then biaxially stretched.
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